Two chains
Why the exchange's timeline and your own history are chained separately, and what each one catches.
Every commitment is linked to the one before it, in two independent ways.
The manifest chain
Each manifest carries the hash of the previous one, and a manifest is published every cycle, even when nobody traded (the users root is then 32 zero bytes).
A skipped cycle, a second manifest for the same number, or a rewritten one all break the chain in public view.
Your own chain
Each of your payloads carries the hash of your previous payload, and your sequence number goes up by exactly one each time. If an old payload of yours is dropped or rewritten, your chain stops connecting, and you are the one holding the evidence.
Why both
The manifest chain guards the exchange's timeline. Your chain guards your own published history.
To check both, see Verify the chains.